1. Field of the Invention
The present invention relates generally to dispersants, and in particular, polyamide dispersants for use in high-electrolyte agricultural solutions.
2. Description of the Related Art
The active ingredients in many agricultural applications are largely hydrophobic or water-insoluble in character and are, by necessity, often administered as finely divided solids suspended in aqueous media. The majority of these active ingredients are manufactured and marketed in concentrated forms which are then diluted prior to application. For example, the active ingredient is typically available in the form of a Suspension Concentrate (SC), Wettable Powder (WP) or Water Dispersible Granule (WG). Although solid formulations such as WP's and WG's are attractive not only from a loading delivery viewpoint, but also from an Occupational Health and Safety viewpont, not all agrochemicals can be formulated into solid formulations. Therefore liquid formulations such as SC's are an important formulation type. The addition of a suitable dispersant in SC formulations is essential in order to achieve a homogenous dispersion. Furthermore, once a homogenous dispersion is achieved, the resulting suspension must remain stable for sufficient time, at least, to allow application by usual means such as spraying. Any settling, agglomeration or flocculation of the solid in the SC formulation may lead to inconsistent and ineffective application as well as blockage of the spraying equipment. It is therefore necessary to provide a dispersant, which gives easy and homogenous dispersion and results in a suspension, which maintains its stability during prolonged storage or storage at elevated temperatures.
It is often desirable to suspend a water-insoluble solid active ingredient in a high-electrolyte (salt) solution, such as a fertilizer or particularly in the case of agrochemical formulations, to combine two active ingredients together in one formulation where one of the active ingredients is a solid dispersion while the other is an electrolyte solution. Solid dispersions in SC formulations in agrochemical applications are generally made using conventional dispersants such as ethylene oxide/propylene oxide block copolymers, tristyrylphenol ethoxylate derivatives, naphthelene suphonate condensate salts, and polymeric comb co-polymers, polyarylsulphonate condensates, alkylether phosphates and ether sulphates, and lignosulphonates. Although these dispersants afford stable SC's exhibiting no sign of sedimentation or crystal growth in non-electrolyte solutions, they fail as dispersants at high electrolyte solutions, leading to particle agglomeration and flocculation.
In some high-electrolyte solutions, lignosulfonates have been utilized as dispersants, however, they display poor dispersing properties. Large amounts of the dispersant are required in order to obtain a stable dispersion, which increases the cost of the dispersion. Furthermore, in higher electrolyte concentrations, or alternatively when high levels of the water insoluble active is required in the electrolyte solution, lignosulfonates fail to prevent particle agglomeration and flocculation.